Manufacture of screw propellers



1 Nov. 1, 1927.

H. LEITNER MANUFACTURE oF scREw PROPELLERS .Filed April 24; 1926inventor? the butt to Patented Nov. l, 1927.

UNITED STATES 1,647,920 r OFFICE.

HENRY LEITN'ER, 0F CBOYDON, ENGLAND.

MANUFACTURE 01! SCREW PROPELLERS.

Application filed April 24, 1926, Serial no.

Fig. l is a side view showing a blank for" apropeller blade arrangedrelatively to the bed of a milling machine and cutter thereof foreffecting one of the stages in the manufacture of the improved blade;

Fig. 2 is a view of the cutter at right angles to that shown in Fig. 1;

Fig. 3 is a plan of a blade blank illustrating a modified stage in themanufacture, and

Fig. i is a view of two milling cutters therefor;

Fig. 5 is a view of another milling cutter illustrating a modificationin the manufacture of a propeller blade.

0; is the simple or composite plate or block of metal or non-metallicmaterial which is shaped to provide the working or acting faces of apropeller blade; for instance, the block is faced or machined flat onone side I), which face may or may not be parallel to the opposite face,and clamped onto the bed 0, Fig. 1, of a milling machine with the flatface downwards, in such a manner that, with reference to the said flatface, the

end d, which will ultimately be the tip of the blade, is higher than theother end by a predetermined amount. The flat face may have beenpreviously cut on the taper relative to the other or upper face in sucha way that the latter is parallel to the bed of the machine when set up.A cut or cuts is then taken along the length of the block with a shapedmilling cutter e, or gang of cutters, acting on the other face i of theblade, the direction of travel of the said outter or cutters beingparallel to the bed of the machine. The millingcutter is shaped te'thelargest section of the finished blade, which will be located at the buttend g of the blade. As many cuts as necessary are taken until the bladeis of the required thickness, which/ thickness will vary from the tip indirect proportion to the inclination of the machined face. The dot anddash lines 6 b, in Fig. 2, indicate,

respectively, the flat face of the blade at the tip and butt.

The leading and trailing edges of the blade, or, in other Words, thewidth of the 104,449, ahd in Great Britain June as, 1924.

blade, will automatically be determined by the shape of the cutter eandthe inclination of the block. Conversely, the inclination of the blockwill be determined by the shape of the cutter and the widths of theblade. In either case, the blade Will be shaped somewhat likethe'head ofa lance or spear.

,An alternative method to the above described is to use the same cutteras described but to cut the blade equal in width and thicknessthroughout its length, and then to plane the face at an inclination tothe back.

Up to this stage I have produced a blade.

correct in section and track, but 'without twist, and this latter isplication of a torque.-

Should it be found desirable to vary the rate of ta er of the blade, forexample, a. section at alf the'length of the blade ma be more than halfthe thickness ofthe extreme butt end section, then the face which hasbeen described as flat could be curved by machining. I

Insteadof shaping the face f of the blade completely at one cut aspreviously described, I may proceed as follows, that is to say, I make acut or cuts in the blade with two or more cutters. As shown in Fig. 4the cutter 18 shaped over the distance as at n to suit the leading edgeand as at n for the trailing edge of the blade, the position of theblank being re-set after the cut or cuts from one edge are made toenable the cut or cuts for the other edge to be made. The path of travelof the cutters may or may not be parallel to each other and to thecenter line of the resulting blade as seen in plan view. In Fig. 3, the

catc two paths of the cutters out of paral- -lelis m.

An alternative method consists in the use of a single tool such as aplaning or shaping tool. Inthis case at each successive cut, the toolmust be raised or lowered, relatively to the face of the blade,'inaddition to being moved in a transverse direction. This set ting of thetool can be arranged by a suitable. cam motion or by han If the otherside of the blade is required to be curved, it is only necessary toreverse the blank and carry out similar operations on that side.

Instead of the straight cuts described above, I may twist or turn theblank longitudinally prior to machinin which twist would enable the mostdesira 1e part of the.

provided by the apdot and dash lines indicutter to operate. For example,when considering the tiprof the blade as cut by a single cutter e, aspreviously described with reference to Fig. 1, the resultant shape israther too thin and sharp for practical work, as indicated by the dotand dash line 0, Fig. 5. If, however, the blank is twisted, advantagecan be taken of the greater camber at one side of the cutter e, the sideproducing the leading edge of the blade, and a better section results,this being indicated by the dot and dash line p Fig. 5.

After one or any combination of the above operations has or have beencompleted, the blade is twisted to the correct helical twist ashereinbefore described and any forward rake necessary can be impartedeither by a torque or by pressure, preferably, when the material is inits softest state.

Claims:

1. A process of manufacture of a screwpropeller blade from a solid blockor blank of metal or" approximately the shape of the blade, consistingin machining one side of the blank flat, securing the blank with themachined surface downward on the bed of a milling machine with the enddesigned to form the tip of the blade higher than the other end, shapingthe upper surface of the blade by two or more operations of millingcutters traveling arallel to the bed of the machine and by wliichdiflerent parts of the blade are shaped.

2. A process of manufacture of a screwpropeller blade from a solid blockor blank of metal of approximately the shape of the blade, consisting inmachining one side of the blank fiat, securing the blank with themachined surface downward on the bed of a planing or shaping machinewith the end designed to form the top of the blade higher than the otherend, shaping the upper surface of the blade by a planing or shaping tooltraveling parallel to the bed of the machine and raised, lowered andmoved transversely automatically or by hand according to the contourrequired for the said face.

3. A modification of the process claimed in claim 1, wherein the blankis twisted throughout the whole or a portion of its length prior to thecutting operation to take advantage of the varying camber of the cutter,and wherein the correct twist for pitch is imparted in a subsequentoperation.

HENRY LEITNER.

